Mixer structure for distributing molten material

ABSTRACT

A structure which includes a convoluted conduit formed in a compact, preferably circular, metal body, such body being superposed on a compact spinneret body, both of which are mounted within a unitary supporting structure. The conduit contains stationary mixing blades extending in series within the conduit, each blade being curved so as to rotate material as it flows through the conduit. The blades are arranged in alternating right and left handed curvature groups (a group consisting of one or more elements). The embodiment shown is made with two convoluted conduit portions, each disposed circularly adjacent the outer perimeter of the first-mentioned body. These two portions are substantially parallel to each other and superposed along the axis of such body.

United States Patent [.191 Devellian et al.

[4 1 Apr. 23, 1974 MIXER STRUCTURE FOR DISTRIBUTING MOLTEN MATERIAL [75] Inventors: Richard D. Devellian, Rockport;

Paul F. Herman, Peabody, both of Mass.; Wilhelm A. Keller, Zurich, Switzerland [73] Assignee: Kenics Corporation, Danvers, Mass.

[22] Filed: June 5, 1972 [2]] Appl. No.: 259,477

[52] US. Cl. 259/4, 425/198 [51] Int. Cl B0lf 15/02 [58] Field of Search 259/4, 18, 36, 185; 1 425/197, 198

[5 6] References Cited UNITED STATES PATENTS 3,325,150 6/1967 Broders 259/1 3,635,444 l/l972 Potter 259/4 3,701,619 10/1972 Appeldoorn 425/198 3,704,006 11/1973 Grout .L ..259/4 Primary ExaminerRobert W. Jenkins [57] ABSTRACT A structure which includes a convoluted conduit formed in a compact, preferably circular, metal body, such body being superposed on a compact spinneret body, both of which are mounted within a unitary supporting structure. The conduit contains stationary mixing blades extending in series within the conduit, each blade being curved so as to rotate material as it flows through the conduit. The blades are arranged in alternating right and left handed curvature groups (a group consisting of one or more elements). The embodiment shown is made with two convoluted conduit portions, each disposed circularlyadjacent the outer perimeter of the first-mentioned body. These two portions are substantially parallel to each other and superposed along the axis of such body.

4 Claims, 2 Drawing Figures MIXER STRUCTURE FOR DISTRIBUTING MOLTEN MATERIAL I Background of the Invention 1. Field of the Invention A device through which molten highly viscous liquids, such as molten polymers or molten glass, flow, which device alters the flow pattern of such'liquid so as to compensate for any difference in the previous thermal history of each particle thereof, during a critical portion of its processing history so as to produce a more homogeneous end product.

2. Problems of the Prior Art The copending'application of Grout and Devellian, Ser. No. 134,317 filed Mar. 15, 1971, describes a device of the kind described above. However, in some applications of such a device, the spatial requirements are such that a much more compact structure than that shown in said copending application is needed. Also where it is desired to maintain the device along its total length within substantially the same temperature environment, the distance between the inlet and outlet ends 7 of the device may tend to introduce an undesirable difference in temperature between different points along the device which must be balanced by a closely controlled temperature environment over such extended distance.

SUMMARY OF THE INVENTION The present invention substantially eliminates the limitations of the prior art by locating mixer elements, of the type described in said copending-application, in a convoluted conduit formed in a block of a material having a relatively high specific heat and a relatively low thermal conductivity. This block may be in the shape of a flat disc or other configuration which may be mounted in a compact assembly in close proximity to a processing unit such asa spinneret, through which the molten material is spun into highly uniform fibers.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical cross-section, taken along line l-l of FIG. 2, of a spinneret incorporating the invention.

FIG. 2 is a horizontal cross-section taken along the line 22 of FIG. 1.

DETAILEDDESCRIPTION OF THE INVENTION The present invention is illustrated in FIGS.'1 and 2 as being incorporated in a spinneret indicated generally at 1. In this arrangement, a molten polymer, to be spun into filaments, is pumped into the spinneret through passage 2, and passes successively through filter 3 resting on support plate 4, the thermal equalizer structure 5, which constitutes the principal feature of this invention, and a spinning nozzle plate 6.

The entire structure is contained within an outer cylindrical housing 7, the upper end of which is closed by a wall 8 through which passage 2 is bored. The several elements previously recited are contained with an inner cylindrical housing 9 which fits snugly within housing 7. Housing 9 is provided with a lower ledge 10 against which the nozzle plate 6 is sealed after having been inserted through the upper open end of housing 9. Nozzle plate 6 is provided with a plurality of bores 11 each terminating in a fine nozzle 12 through which the molten polymer is ejected to solidify into filaments.

The thermal equalizer 5, which rests on the nozzle plate 6, is constructed of three flat metal disks 13, 14, and 15. It will be noted that FIG. 2 includes a view of the bottom face of disk 13. This disk 13 has a plenum 16 formed in its upper face portion, with a central passage or port 17 extending from said plenum to a convoluted groove 18 formed in the lower face portion of disk 13.-The convolution of groove 18, which is one example of the configuration of such groove, extends outwardly from passage 17 to a substantially circular portion near the outer edges of disk 13. Groove 18 also is made with a substantially semicircular cross-section.

Disk 14 has formed in its upper face portion a convoluted grooves 18a which is of the same shape as groove 18 and which matches with groove 18 to form a cylindrical convoluted passage in the combined thermal equalizer 5 when the disks 13 and 14 are assembled as shown in FIG. 1. Groove 18a however differs from groove 18 in that, instead of having a central passage corresponding to passage 17, its outer end terminates at a passage 19 drilled through disk 14 to its lower face portion. The lower face portion of disk 14 also has formed therein a convoluted groove 20 shaped substantially like grooves 18 and 18a and extending from said passage 19 to terminate at substantially the center of disk 14. Disk 15 has a similar convoluted groove 20a matching groove 20 so as to form a cylindrical convoluted passage when the disks 14 and 15 are assembled as shown in FIG. 1. However, groove 20a, where it matches with the central end of groove 20, terminates at a passage or port 21 drilled through disk 15 to connect with a flared conical opening 22. Disk 15 is provided with a spacer ring portion 23 which rests on the nozzle plate 6 to provide a plenum into which the molten polymer is distributed as it flows out of conical opening 22. Thereupon the molten polymer enters the bores 11 and is spun out of the nozzle 12.

In order to compensate for any differences in the previous thermal history of the particles of polymer delivered to the spinneret structure, a series of twisted mixer blades 25 and 26 is mounted in the circular convoluted shown in FIG. 2, as the polymer flows in the direction of thearrows from passage 17, it will first encounter a blade 25 which is twisted in a left-hand direction. As the polymer leavesblade 25 it encounters a blade 26 which is twisted in a right-hand direction. Such succession of left-hand and right-hand twisted blades 25 and 26 is continued throughout channel 18-18a until it ends where the polymer leaves the last blade 26 and enters the passage 19. When the polymer flows through passage 19 it enters convoluted channel 20-20a in which is located a similar series of left-hand and right-hand twisted blades 25 and 26. After the polymer has been subjected to the action of the mixer blades in both convoluted channels, it passes out through passage 21 and conical opening 22 to be spun through nozzles 12 as described above.

Each cross-section of each mixer blade 25 and 25 lies along the diameter of a circle, which diameter may equal the inner diameter of the channels 18-l8a and 20-20a. The length of each blade may be up to several times its width but is preferably equal to its width. The adjacent edges of successive elements are disposed at a substantial angle, preferably with respect to each other. Although in the preferred embodiment each blade is twisted in the opposite direction to that of the preceeding blades, other configurations for causing reversal of spin of the flowing material may be used. For example, a plurality of blades twisted in one sense may be followed by a plurality of blades twisted in the opposite sense. Therefore, the blades may be considered as being arranged in alternating right-handed and lefthanded curvature groups, it being understood that a group may consist of one or more blades.

. The fabrication of each blade 25 and 26 is simplified and its fitting within its channel made more accurately if the longitudinal axis of each such blade lies along a straight line. For this purpose each of the channels l8-l8a and 20-20a, along each length into which a mixer blade 25 or 26 is to be inserted, is formed as a short section of a straight cylinder, as shown in FIG. 2.

.The length of each such section corresponds 'to the length of one of the blades 25 or 26 so that such blades fit easily and accurately into such lengths.

The support plate 4 is also formed with a spacer ring 27 which rests on top of disk 13. The filter 3 is retained against the top of support plate 4 by a spacer ring 28 formed on a cap member 29 provided with a central passage 30 which is maintained in alignment with passage 2. The entire assembly within the housing 9 is held in place by an externally threaded clamping nut 31 which is threaded into threaded end 32 of housing 9 and seats against a shoulder 33 of cap member 29.

The above assembly is retained within the outer housing 7 by a retaining ring 34 held in place by a series of bolts 35 threaded into the lower end of housing 7. To insure a tight seal between passages 2 and 30 a gasket 36 may be used.

In order to further maintain uniform temperature conditions in the structure as well as for reasons of strength, the disks l3, l4 and are made ofa material of high thermal inertia such as steel, preferably carbon steel, which possesses relatively high heat capacity and relativelylow thermal conductivity.

Specific heat (S) may be expressed in British Thermal Units (BTU), per pound (lb) of the material, per degree Fahrenheit (F), as follows:

s =-BTU/(lb F) Thermal conductivity (K) may be expressed in British Thermal Units (BTU), per hour (h) per square foot (ft through which heat flows, per degree Fahrenheit (F), per inch (in) of distance through the material as follows:

K BTU/[hr Xft (F/in)] In the present specification and claims, relatively high specific heat means a value of S between about 0.1 and 0.4, and relatively low thermal conductivity" means a value of K between about 50 and 120.

devices of this kind, which do not use the novel mixing structure of this invention, produced undesirable variations in the quality of the fiber spun by the device. The

use of the present invention eliminates such variation as will be described below.

Due to the complex mixing action exerted upon the flowing polymer, particles of polymer are thoroughly mixed and each particle of that polymer is subjected to substantially equal accelerations and decelerations so as to produce substantially the same residence-time for each particle in its travel through the thermal equalizer 5. The detailed nature of this complex mixing action is described in greater detail in said copending application. Also the convoluted form of the conduit in which the mixer blades are placed causes such action to occur within a compact structure, which may be assembled in intimate relation with the rest of the system without any undue increase in spatial requirements. The resulting compactness makes it relatively simple to maintain the desired constant thermal environment for the whole system, particularly since each convoluted passage is 'buried in a material of relatively high specific heat and relatively low thermal conductivity. The term convoluted in the specification and claims herein is intended to cover any kind of folded, coiled, curved or other shape which substantially reduces the distance betweenthe ends of a conduit over that which exists in a rectilinear form of such conduit.

Various modifications of the structure illustrated may be made. For example, a well known shear compensator may be interposed between the thermal equalizer 5 and the spinneret 6. Also the filter 3 might be placed in the stream after the thermal equalizer. Other modifications, within the scope of the appended claims will suggest themselves to those skilled in the art.

What is claimed is: A

l. A mixer structure comprising a. an elongated conduit having inlet and outlet ports for the passage of fluid material; b. said conduit being convoluted between said ports;

c. said conduit containing within it a plurality of curved sheet-like elements extending in series along said conduit and each such element havinga .curvature to rotate the material flowing through said conduit, the longitudinal axis of each element being substantially a straight line, said elements being arranged in alternating right and left-handed curvature groups with leading and trailing edges of adjacent elements being disposed at a substantial angle to each other;

. said conduit being formed of a series of short sections of a straight cylinder, and each of said elements being mounted in one of said sections. 2. A mixer structure comprising: I

a. an elongated conduit having inlet and outlet for the passage of a fluid material; b. said conduit being convoluted between said ports;

ports 0. said conduit containing within it a plurality of curved sheet-like elements extending in series along said conduit and each element having a cutvature to rotate the material flowing through said conduit, said elements being arranged in alternating right and lefthanded curvature groups with leading and trailing edges of adjacent elements being disposed at a substantial angle to each other;

d. said conduit being formed within a flat body;

3,806,097 Y 6 e. said conduit comprising at least two serially conbody comprises a block of material having 'a relatively nected convoluted portions, the convolutions of high specific heat and a relatively low thermal conduceach such portion being disposed substantially on tivity. p a plane, said planes being substantially parallel and 4. A mixer structure as in claim 3 in which the outer superposed in a direction along the axis of said flat 5 border of said flat body conforms closely to the envebody. lope of the convolutions 'of such conduit. 3. A mixer structure as in claim 1 in which said flat 

1. A mixer structure comprising a. an elongated conduit having inlet and outlet ports for the passage of fluid material; b. said conduit being convoluted between said ports; c. said conduit containing within it a plurality of curved sheet-like elements extending in series along said conduit and each such element having a curvature to rotate the material flowing through said conduit, the longitudinal axis of each element being substantially a straight line, said elements being arranged in alternating right and left-handed curvature groups with leading and trailing edges of adjacent elements being disposed at a substantial angle to each other; d. said conduit being formed of a series of short sections of a straight cylinder, and each of said elements being mounted in one of said sections.
 2. A mixer structure comprising: a. an elongated conduit having inlet and outlet ports for the passage of a fluid material; b. said conduit being convoluted between said ports; c. said conduit containing within it a plurality of curved sheet-like elements extending in series along said conduit and each element having a curvature to rotate the material flowing through said conduit, said elements being arranged in alternating right and left-handed curvature groups with leading and trailing edges of adjacent elements being disposed at a substantial angle to each other; d. said conduit being formed within a flat body; e. said conduit comprising at least two serially connected convoluted portions, the convolutions of each such portion being disposed substantially on a plane, said planes being substantially parallel and superposed in a direction along the axis of said flat body.
 3. A mixer structure as in claim 1 in which said flat body comprises a block of material having a relatively high specific heat and a relatively low thermal conductivity.
 4. A mixer structure as in claim 3 in which the outer border of said flat body conforms closely to the envelope of the convolutions of such conduit. 